Routes - custom subdomains and adding admin namespace

I set up my rails app to use custom subdomains following this awesome RailsCast tutorial by Ryan Bates. Users can visit company.lvh.me:3000 and view all its relevant information. Now, I would like to add an admin subdomain on the front of the custom subdomain (admin.company.lvh.me:3000).

The idea is that I have specific admins for each blog with special controllers/views. So if admin is added to the front of the company subdomain, rails will route through the app/controllers/admin/blogs_controller.rb and show the app/views/admin/blogs/show.html.erb.

I've used the admin namespace and set it as a subdomain in some of my past Rails apps, but when I try that here I need the second subdomain to be dynamic:

So if type admin.company in the subdomain constraint, it works like a charm, but how can make it dynamic? I've had no luck making it dynamic ('admin.' + Subdomain, etc.) in the routes files, which lead me to the thought: can I just use Ryan Bates's Subdomain class?

I'm actually using the 'show' action in this situation as the 'home' page for the blog and I set the blog according to the subdomain (not an id passed as a parameter). It feels a little hackish, but I was able to get it working: